Unsteady flow over an airfoil inside a wind tunnel with and without transpiration

1986 ◽  
Author(s):  
W. TEDESCHI ◽  
D. WILSON
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow

scholarly journals Introduction of Multi-fan Unsteady Flow Wind Tunnel

2021 ◽  
Vol 46 (1) ◽  
pp. 40-44
Author(s):  
Yumi IIDA ◽  
Daisuke SOMEKAWA
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow

Lift and Measurements in an Aerofoil in Unsteady Flow

1973 ◽  
Author(s):  
D. W. Holmes
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow ◽  
Pressure Distribution ◽  
Pressure Fluctuations ◽  
Separation Region ◽  
Vortex Theory

A wind tunnel is described which is capable of producing both “transverse” and “streamwise” gusts. An account is given of the lift and pressure fluctuations measured on an isolated aerofoil tested in the tunnel. The response to a transverse gust compares well with Kemp’s (1) theory although the pressure distribution is not as predicted. The results suggest that the wake behavior and in particular the existence of a separation region can in practice seriously affect the validity of applying the now classical unsteady vortex theory.

UNSTEADY-FLOW TESTING IN A LOW-CORRECTION WIND TUNNEL

1998 ◽  
Vol 12 (1) ◽  
pp. 33-45 ◽  
Author(s):  
L. KONG ◽  
M. HAMEURY ◽  
G.V. PARKINSON
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow

Utilizing Bi-Stability to Improve the Performance of Wake-Galloping Energy Harvesters in Unsteady Flow

2016 ◽  
Author(s):  
Ali H. Alhadidi ◽  
Mohammed F. Daqaq ◽  
Hamid Abderrahmane
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow ◽  
Output Power ◽  
Bluff Body ◽  
Unsteady Flows ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Restoring Force ◽  
Energy Harvesters ◽  
Piezoelectric Cantilever

This paper investigates exploiting a bi-stable restoring force to enhance the transduction of wake-galloping energy harvesters in unsteady flows. To that end, a harvester consisting of a piezoelectric cantilever beam augmented with a square-sectioned bluff body at the free end is considered. Two repulsive magnets located at the tip of the beam are used to introduce the bi-stable restoring force. Unsteadiness is generated in a wind tunnel using static-grid structures located in the upstream of the bluff body. Three different mesh screens with square bars are designed with different bar and mesh widths to control the Reynolds numbers and associated unsteadiness. A series of wind tunnel tests are then used to experimentally investigate the response of the harvester with and without the tip magnets. Results demonstrate that the bi-stable restoring force can be used to improve the output power of the harvester under unsteady flow conditions.

scholarly journals Nectar vs. pollen loading affects the tradeoff between flight stability and maneuverability in bumblebees

2015 ◽  
Vol 112 (33) ◽  
pp. 10527-10532 ◽  
Author(s):  
Andrew M. Mountcastle ◽  
Sridhar Ravi ◽  
Stacey A. Combes
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow ◽  
Resource Selection ◽  
Center Of Mass ◽  
Equal Mass ◽  
Moment Of Inertia ◽  
Flight Performance ◽  
Rotational Moment ◽  
External Perturbations ◽  
Smooth Flow

Bumblebee foragers spend a significant portion of their lives transporting nectar and pollen, often carrying loads equivalent to more than half their body mass. Whereas nectar is stored in the abdomen near the bee’s center of mass, pollen is carried on the hind legs, farther from the center of mass. We examine how load position changes the rotational moment of inertia in bumblebees and whether this affects their flight maneuverability and/or stability. We applied simulated pollen or nectar loads of equal mass to Bombus impatiens bumblebees and examined flight performance in a wind tunnel under three conditions: flight in unsteady flow, tracking an oscillating flower in smooth flow, and flower tracking in unsteady flow. Using an inertial model, we estimated that carrying a load on the legs rather than in the abdomen increases a bee’s moment of inertia about the roll and yaw axes but not the pitch axis. Consistent with these predictions, we found that bees carrying a load on their legs displayed slower rotations about their roll and yaw axes, regardless of whether these rotations were driven by external perturbations or self-initiated steering maneuvers. This allowed pollen-loaded bees to maintain a more stable body orientation and higher median flight speed in unsteady flow but reduced their performance when tracking a moving flower, supporting the concept of a tradeoff between stability and maneuverability. These results demonstrate that the types of resources collected by bees affect their flight performance and energetics and suggest that wind conditions may influence resource selection.

Characteristics of unsteady flow around two successive rectangular ribs on floor of a wind tunnel

2017 ◽  
Vol 65 ◽  
pp. 450-458 ◽  
Author(s):  
G.K. Ntinas ◽  
I.N. Dados ◽  
X. Shen ◽  
N.A. Malamataris ◽  
V.P. Fragos ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow

scholarly journals The Influence of Different Unsteady Incident Flow Environments on Drag Measurements in an Open Jet Wind Tunnel

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 178
Author(s):  
Xiao Fei ◽  
Christoph Jessing ◽  
Timo Kuthada ◽  
Jochen Wiedemann ◽  
Andreas Wagner
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow ◽  
Pressure Gradient ◽  
Test Section ◽  
Static Pressure ◽  
Signal Amplitude ◽  
Correction Method ◽  
Scale Model ◽  
Signal Frequency ◽  
On The Road

Aerodynamic development for road vehicles is usually carried out in a uniform steady-state flow environment, either in the wind tunnel or in Computational Fluid Dynamics (CFD) simulations. However, out on the road, the vehicle experiences unsteady flow with fluctuating angles of incidence β, caused by natural wind, roadside obstacles, or traffic. In order to simulate such flow fields, the Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (FKFS) swing® system installed in the quarter scale model wind tunnel can create a variety of time-resolved signals with variable β. The static pressure gradient in the empty test section, as well as cD values of the Society of Automotive Engineers (SAE) body and the DrivAer model, have been measured under these transient conditions. The cD measurements have been corrected using the Two-Measurement Correction method in order to decouple the influence of the unsteady flow from that of the static pressure gradient. The investigation has determined that the static pressure gradient in the empty test section varies greatly with different excitation signals. Thus, it is imperative to apply a cD correction for unsteady wind tunnel measurements. The corrected cD values show that a higher signal amplitude, as in, signals with large β, lead to higher drag forces. The influence of the signal frequency on drag values varies depending on the vehicle geometry and needs to be investigated further in the future.

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